Solved! I decided to blend the 6 mg Boro with a 3 mg Kalhua, in a 2 part Kalhua to 1 part Boro ratio, in order to end up with a 4 mg Kahlua/Boro Blend.
I first mixed up the 3 mg Kahlua:
1/4 tsp Fairie's Finest Creme De Cafe extract
1/4 tsp 24 mg tasteless e-liquid
1/4 tsp distilled water
1 1/4 tsp glycerine
Then I mixed 1 tsp of the above 3 mg Kahlua with 1/2 tsp of the Boro. (This left some 3 mg Kahlua for later use.) The Kahlua alone gives a very dry flavor, reminiscent of a Turkish tobacco. Blended in a 2:1 ratio with the Boro, the tobacco flavor of the Boro remains as an undertone, while the celery flavor has completely disappearred.
Now to find some menthol crystals. I would LOVE to try the above with one or two drops of mentholated concentrate.